1. Field of the Invention
The invention relates to cases made from cardboard, corrugated board, or similar sheet material as well as the blanks of such material for forming said cases and a machine for producing said cases from said blanks.
2. Description of the Prior Art
From the patents U.S. Pat. No. 4,242,949, DE-A-3 541 821 and FR-A-2 629 012, for example, machines are known which are capable of producing a cardboard case or similar by wrapping a blank about a mandrel. In these machines, said mandrel has an essentially square or rectangular cross section, so that the cases obtained have four lateral faces defining a volume whose cross section, parallel to the bottom of said cases is also square or rectangular. Of course, two adjacent lateral faces are then orthogonal to each other and form an edge perpendicular to the bottom of the case.
Such cases are used for packing objects or groups of objects which are introduced therein through the lid which remains open, said lid only being closed after introduction of said objects.
It rarely, if ever, happens that the cross section of the load formed by said objects or groups of objects is square or rectangular and is exactly adapted to that of the case in which said load is introduced, so that said load is not firmly held in said case by the lateral faces thereof and the corners of the case are projecting and empty. The result is that the load may move inside the case, causing instability leading to difficulties in handling and loading on a transport means. In addition, the projecting corners of the case are exposed to external aggressions and may be easily torn, which adversely affects the presentation and protection of the packed products. Finally, the empty corners of the case form a waste of sheet material, since they are useless.
To partially overcome these drawbacks, the patent U.S. Pat. No. 4,308,029 proposes disposing an object to be packed inside said mandrel and wrapping the blank, under tension and with resilient deformation of two opposite lateral faces of the case. Thus, a square cross section package is obtained whose faces are exactly tangential to the walls of said object.
It will be noted that use of the machine described in this latter patent raises problems when a group of objects (and not a single object) are to be packed in the case. In addition, the package obtained also has projecting and empty corners, likely to be damaged and useless.